Re: DS1820 temp sensor odd results

Eric Yancey wrote:

Hello,

I recently installed a temperature monitoring system for my home workshop.
The primary goal is to monitor the heat capacity and dissipation of a
concrete slab floor with radiant heat tubing. When I installed the heating
tubes before the concrete was poured, I embedded a fairly short (5 feet or
so) piece of PEX tubing to house a temperature sensor.

I built kit 145 from here: http://kitsrus.com/kits.html to interface with
four dallas DS18S20 sensors. One sensor measures ambient air temp, two
measure the temperature of the fluid entering and exiting the floor, and the
fourth is inserted in the terminated PEX tube as described above.

The problem I'm having is that the 4th sensor is reporting flaky results. I
replaced the original sensor but the replacement is exhibiting the same
behavior as the original. Here is some sample data:

07:45:00 78.35
07:44:30 74.07
07:44:00 71.15
07:43:30 72.50
07:43:00 75.20
07:42:30 67.42
07:42:00 74.62
07:41:30 67.32
07:41:00 75.97
07:40:30 71.15
07:40:00 73.96
07:39:30 69.80
07:39:00 69.80
07:38:30 78.01
07:38:00 73.96
07:37:30 57.87
07:37:00 70.57

02:01:00 61.25
02:00:30 86.11
02:00:00 84.76
01:59:30 59.56

Around midnight the sensor was reporting temperatures consistently around
60F which I believe is the actual temperature of the slab. From around
2:00AM this morning it started reporting inconsistent values, and now,
around 8:00AM, it is reporting temperatures anywhere from 57F to 78F, which
I know is not correct (the temp of a concrete slab cannot fluctuate 30
degrees in 8 minutes).

Does anyone have any ideas on why this may be happening?

I apologize for the length of the message and thanks for any help!

Eric Yancey


lost soles of those lying in the cement below that slab? :)

Radon gas?, some element mix in the concrete that maybe reacting
to a near by R.F. signal at times?
who knows! :)


--
"I am never wrong, once i thought i was, but i was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

.

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